1. Field of the Invention
The present invention relates to a reformed polypropylene resin composition, a method of producing the same, a mold-stamping material composed of the reformed resin composition, and injection-molded articles thereof. More specifically, the invention relates a reformed polypropylene resin composition having high fluidity, excellent impact strength and rigidity, a method of producing the same, a mold-stamping material composed of the reformed resin composition and injection-molded articles thereof.
2. Description of the Prior Art
In the field of automotive parts, it is becoming essential to reduce the weight to cope with environmental problems on a global scale. In particular, the base resins for producing thin and light-weight products by such a molding method as mold-stamping or the like, must have high degree of fluidity, high degree of rigidity and excellent impact strength property.
To meet such requirements, a lot of improvements have been accomplished and a variety of polyolefin resin compositions have been developed. For instance, a polyolefin resin composition having improved fluidity is obtained by heat-treating a polyolefin resin while adding an organic peroxide thereto. However, the thus obtained polyolefin resin has problems in that it has small rigidity and low impact strength property.
Japanese Laid-Open Patent Publication Nos. 42448/1985 and 233047/1986 disclose polypropylene resin compositions having high degree of fluidity, excellent rigidity and impact strength property at low temperatures that are obtained by blending a crystalline ethylene/propylene block copolymer with an ethylene/propylene copolymer rubber, an inorganic filler and an organic peroxide, and heat-treating them at 170.degree. to 280.degree. C.
When the polypropylene resin composition is processed as described above, however, the crystalline ethylene/propylene block copolymer undergoes the decomposition. Therefore, though the fluidity increases, the rigidity and the impact strength property are not sufficiently improved.